A multiple chamber type semiconductor manufacturing system is constructed as shown in FIG. 1 of the drawings attached hereto. The system has a plurality of process chamber stations 2a, 2b, 2c, 2d and 2e disposed around a transfer chamber 1, and also has arranged therein a pair of workpiece delivery stations 3 by each of which the workpiece is delivered to an outside thereof. The space within the transfer chamber 1 is kept in an evacuated state by a suction unit.
The above mentioned transfer chamber 1 is constructed as shown in FIG. 2 of the drawings attached hereto and has a handling robot A provided at a central region thereof so as to be rotatable. It also is provided with a plurality of partition walls 5 that serve as the peripheral walls thereof. Each wall opposes one of the stations 2a, 2b, 2c, 2d and 2e or the workpiece delivery stations 3. There are also provided a plurality of gates 6 each of which constitutes both an inlet and an outlet for the workpiece to be fed into and out of each of the stations. Each such gate 6 is configured so as to be opened and closed by an opening and closing door (not shown) that is disposed in opposition to each of the gates 6.
As the above mentioned handling robot A, there has hitherto been used an apparatus of a so called frog leg type with a pair of arms, and its construction is as shown in FIGS. 3 to 7 of the drawings attached hereto.
In this construction, the pair of arms, designated as 7a and 7b, have an identical length and are arranged so as to be rotatable about a center of rotation. On the other hand, there are provided a pair of transfer tables 8a and 8b that have respective bases. Each of the transfer tables is connected to a first end of one of two legs of one of two pairs of links 9a and 9b which have an identical length. The first end of each of the two legs of each pair of links 9a and 9b is coupled via a frog leg type transfer table attitude regulating mechanism to one of the transfer tables 8a and 8b, respectively. Therefore, the links 9a and 9b may be rotated in a pair of directions, each of which is completely symmetrical with respect to the said transfer tables 8a and 8b.
Each of the pair of links 9a and 9b which are coupled to the transfer table 8a or 8b are also coupled to one of the said pair of arms 7a and 7b, whereas each of the other pair of links 9a and 9b is coupled to the other one of the arms 7a and 7b, respectively.
FIG. 4A in the drawings attached hereto shows the transfer table attitude regulating mechanism B of the above mentioned frog leg type, in which the respective forward end portions of the links 9a and 9b in the pair which are coupled to the transfer tables 8a and 8b are coupled together in a gear configuration. The gear configuration comprises a pair of gears 9c and 9c which mesh with each other so that the angles of attitude .theta.R and .theta.L of the links 9a and 9b with respect to the said transfer tables 8a and 8b may always be identical to each other. This allows each of the transfer tables 8a and 8b to always be oriented in a radial direction and operated in the radial direction.
It should be noted, however, that the above mentioned links 9a and 9b may not necessarily be coupled together in a gear arrangement, but may alternatively be coupled together with a crossed belting arrangement 9d as shown in FIG. 4B of the drawings attached hereto.
FIG. 5 of the drawings attached hereto shows a mechanism for permitting the above mentioned arms 7a and 7b to be rotated independently of each other.
The respective bases of the arms 7a and 7b are each configured in the form of a ring shaped boss, and such ring shaped bosses 10a and 10b are configured so as to be coaxial about the center of rotation and to be rotatably supported with respect to a frame 1a of the transfer chamber 1.
On the other hand, the said ring shaped bosses 10a and 10b have a pair of disk shaped bosses 11a and 11b disposed therein, respectively, wherein a ring shaped boss and a disk shaped boss oppose each other and are arranged so as to be coaxial with each other. A first pair of mutually opposing ring shaped and disk shaped bosses and a second pair of the mutually opposing ring shaped and disk shaped bosses are coupled and decoupled with each other via each of magnetic couplings 12a and 12b, respectively, in each of the directions of rotation.
The above mentioned pair of disk shaped bosses 11a and 11b have their respective rotary shafts 13a and 13b arranged so as to be coaxial with each other. The said rotary shafts 13a and 13b are coupled to the output sections of a pair of motor units 14a and 14b, respectively. The motor units are coaxial with the frame 1a of the transfer chamber 1, and are supported with their positions deviated in their axial direction.
The above mentioned motor units 14a and 14b have each integrally coupled thereto a motor 15 (which comprises, for example, an AC servo motor) and a speed reduction gear 16 (which comprises, for example, a Harmonic Drive which is a trade name, identically referred to hereinafter). Such reduction gears 16 and 16 have their output sections which are coupled to the respective bases of the rotary shafts 13a and 13b, respectively.
Since the space within the transfer chamber 1 in which the arms 7a and 7b are positioned is held in an evacuated state, there is provided a sealing partition 17 between the ring shaped boss 10a and the disk shaped boss 11a, and between the ring shaped boss 10b and the disk shaped boss 11b of the present arm rotary mechanism.
FIGS. 7A and 7B show an operation of the above mentioned handling robot A. As shown in FIG. 7A, when the two arms 7a and 7b are located at diametrically symmetrical positions with respect to the center of rotation, the links 9a and 9b will be in a state in which they assume their most retracted positions with respect to each of the transfer tables 8a and 8b. Therefore, the transfer tables may both be displaced toward the center of rotation.
In this state, by rotating the two arms 7a and 7b in an identical direction, it can be seen that the two transfer tables 8a and 8b will be rotated about the said center of rotation whilst maintaining the radial positions thereof.
By rotating the two arms 7a and 7b in the directions in which they may approach each other (or in the mutually opposite directions), from the state shown in FIG. 7A, it can be seen that one of the transfer tables 8a (that is located at such a position that the angle made by the two arms 7a and 7b is reduced) will be pushed by the links 9a and 9b so as to be projected in a radially outward direction. Therefore, it may be thrust into one of the above mentioned stations 2a, 2b, 2c, 2d, 2e and 3 which are disposed adjacent to the radially outward side with respect to the transfer chamber 1 as shown in FIG. 7B.
At this point of time, while the other of the transfer tables will be displaced towards the center of rotation, it can be seen that its amount of displacement will be small because of the angle that is made between the arms 7a and 7b and the angle that is made between the links 9a and 9b.
The above mentioned conventional handling robot has been expected to provide a functional effect as a two arm robot by virtue of the advantage that a pair of transfer tables are provided and can alternately or consecutively be used for each of a variety of stations. It has been found, however, that as a matter of reality there arises the following problem.
More specifically, since each of the pair of transfer tables is coupled via a pair of links commonly to a pair of arms, respectively, it has been found that when one transfer table is displaced towards a station, the other transfer table must necessarily be in a stand-by state. This will make it impossible for an individual transfer table to be displaced optionally towards a station.
Also, in a case where a transfer table is to be rotated, a pair of transfer tables must be rotated together, and this makes it impossible for an individual transfer table to be rotated as desired.
From the reasons mentioned above, in spite of the fact that there have specially been provided a pair of transfer tables, it is found that such a provision by itself has not contributed to a desired shortening of the time cycle in a semiconductor manufacturing system that has been provided with a plurality of process chambers around a transfer chamber.
Also, in the above mentioned conventional handling robot, it is noted that a drive mechanism for rotating each of the arms comprises a pair of the motor units 14a and 14b, each of which combines the motor 14 with a speed reduction gear 16 that is high in speed reduction ratio. Since such speed reduction gears 16 and 16 of the motor units 14a and 14b have their output sections which are connected via a pair of the rotary shafts to a pair of the disk shaped bosses 11a and 11b, it has been found that there must be an elongated path of power transmission provided from each of the respective output sections of the said speed reduction gears to a corresponding one of the said disk shaped bosses.
It may also be noted that as shown in FIG. 6 of the drawing attached hereto, there has been another construction of the handling robot in which a pair of disk shaped bosses 11a' and 11b' are provided on the interior with a pair of inner teeth gears 11c and 11d, respectively. A pair of pinion gears 13c and 13d mesh, respectively, with the pair of inner teeth gears.
The pinion gears 13c and 13d are securely fixed to a pair of rotary shafts 13a' and 13b', which in turn are coupled to the speed reduction gears of the motor units 14a and 14b, respectively. Such a construction, however, again requires that there should be provided an elongated path of power transmission from each of the respective output sections of the speed reduction gears to a corresponding one of the disk shaped bosses.
In the drive mechanism of the conventional handling robot, the need for an elongated path of power transmission from a motor unit to a disk shaped boss as noted above has resulted in an insufficiently low torsional rigidity. Also, since a transmission torque is increased at a speed reduction gear that is remote from a disk shaped boss via a rotary shaft, a deformation thereof may give rise to an error in rotation thereof which produces an error in the rotary angle of an arm. Thus, a bottle neck in accurately controlling the rotary angle of the handling robot in the prior art is produced.
It may also be noted that a handling robot to be used in a clean room or an evacuated state in an above mentioned semiconductor manufacturing system requires that very little dust should be introduced therein so that no foreign matter may adhere to an object being conveyed.
In a conventional handling robot as generally mentioned above and particularly as shown in FIG. 8 of the drawings attached hereto, a transfer table 8 that enters into and comes out of each of the stations 2a-2e via a said gate 6 is coupled to a pair of the arms 7a and 7b via the transfer table attitude regulating mechanism B of a frog leg type having a pair of rotary nodes. However, it has been found that there arises the problem that a portion of a gear transmission mechanism or a belt transmission mechanism which is included in the transfer table attitude regulating mechanism B may be a source of dust from which dust can develop. A further problem has been that such a portion also tends to be loosened, giving rise to a positioning inaccuracy.
Accordingly, the present invention has been made with the foregoing problems taken into account. Its generic object is to provide a handling robot whereby the cycle time for a manufacturing operation can be shortened by permitting an action for conveying each of a plurality of transfer tables into and out of each of the stations, and whereby this action can be carried out independently of the other transfer tables. The accuracy at which an arm is rotated in a controlled manner can be enhanced by not permitting any error within the path of power transmission to influence the control of the rotary angle of the arm.
A further important object of the present invention is to provide a handling robot whereby dust that may be produced at a coupling portion between a transfer table and an arm can be reduced to a very minimum, and any loosening that may develop at the coupling portion can also be reduced to a very minimum.